Dengue (DEN) and DEN hemorrhagic fever (DHF) are extremely important diseases of humans throughout the tropical and neotropical regions of the world. Substantial information has accrued concerning the molecular biology of the DEN viruses and the population genetics of their mosquito vectors, but there is little understanding of genetic factors and associations that pose significant risk for human infections with this important pathogen. In these studies, molecular techniques, such as the polymerase chain reaction (PCR), single strand conformational polymorphism (SSCP) analysis, and random amplified polymorphic DNA (RAPD-PCR) to investigate genetic determinants of Aedes aegypti - pathogen interactions and to identify risk factors and develop biomarkers for DEN transmission. RAPD-PCR and SSCP/sequence analysis of mitochondrial genes will be used to determine gene flow and examine phylogenetic histories among Ae. aegypti populations in Mexico and the contiguous United States. These studies will permit an assessment of rates and patterns of gene flow among Ae. aegypti populations, thereby identifying possible trafficking routes of vectors. SSCP and sequence analyses will be used to determine the extent of genetic variability and phylogenetic relationships among DEN viruses from Mexico. Epidemiologically significant viruses will be genotyped and biomarkers correlated with transmission potential and virulence will be determined. Overall, we will effect a marriage of cutting edge molecular and population genetic techniques with epidemiologic and laboratory studies to elucidate risk factors for DEN/DHF in North America The proposed studies will provide insight in DEN-vector interactions and DEN epidemic potential and biomarkers of populations of Ae. aegypti and DEN that pose maximum potential for DEN virus transmission in North America. Such information would be invaluable and would permit public health agencies to focus control efforts on areas where the risks for DEN/DHF are greatest.